Composite foundation member and method

ABSTRACT

THE INVENTION RELATES TO A FOUNDATION ELEMENT OR MEMBER OF AN OFFSHORE PLATFORM NORMALLY POSITIONED IN AN ANCHORING MEDIUM TO ELEVATE THE PLATFORM A PREDETERMINED DISTANCE ABOVE SAID MEDIUM. THE FOUNDATION ELEMENT COMPRISES A FIRST OR OUTER CASING DISPOSED IN A GENERALLY UPRIGHT POSITION AND BEING OPERABLY OR FIXEDLY CONNECTED AT THE UPPER END TO THE PLATFORM. THE OPPOSED LOWER END OF THE FOUNDATION ELEMENT COMPRISES A PILE OR SIMILAR MEMBER ADAPTED TO BE FORCEFULLY IMBEDDED   IN THE ANCHORING MEDIUM. THE LATTER MEMBER IS GUIDABLY POSITIONED IN THE CASING AND IS FASTENED TO THE CASING AT A PERIPHERAL INTERLOCKING JOINT TO FORM THE TWO CONCENTRIC MEMBERS INTO A UNITARY BODY.

`Fan. 19, 1971 c. PoGoNowsKl COMPOSITE FOUNDATION MEMBER AND METHOD Filed Sept. 16,- 1968 l United States Patent O 3,555,831 COMPOSITE FOUNDATION MEMBER AND METHOD Ivo C. Pogonowski, Houston, Tex., assignor to Texaco Inc., New York, N.Y., a corporation of Delaware Filed Sept. 16, 1968, Ser. No. 759,964 Int. Cl. E02b 17/00; E02d 21 00; B21d 39/04 U.S. Cl. 61-46.5 9 Claims ABSTRACT F THE DISCLOSURE The invention relates to a foundation element or member of an offshore platform normally positioned in an anchoring medium to elevate the platform a predetermined distance above said medium. The foundation element comprises a first or outer casing disposed in a generally upright position and being operably or fixedly connected at the upper end to the platform. The opposed lower end of the foundation element comprises a pile or similar member adapted to be forcefully imbedded in the anchoring medium. The latter member is guidably positioned in the casing and is fastened to the casing at a peripheral interlocking joint to form the two concentric members into a unitary body.

BACKGROUND OF THE INVENTION Offshore structures of the type contemplated are utilized primarily in an oil producing or drilling installation wherein a platform is supported above either the land or the ocean surface. In the instance of an offshore facility, one or more legs extending from the platform into the water, are fixed to the ocean floor by piles connected to the legs. Normally a rigid connection is maintained between the concentrically arranged pile and leg by cementing or grouting an overlapping section of the two members for a length of or more feet depending on the weight to be supported and the depth of the water. Such grouted joints however, do not always properly rigidize the structure, which are often weakened due to grout contamination, improper curing and similar conditions. A failure of this type below diver access level can render the joint unsafe and the plaform perhaps unusable. Further, during the installation of the support members, the step of cementng or grouting of the leg to the piling is a protracted operation since the nature of the cement is such that hardening and curing will occur only over a period of time.

In forming such cemented joints, it is usually necessary to provide a flow control system of piping from the waters surface, to the grouted joint whereby the cement might be directed to the latter. This condition, when considered for deep water operations, can prompt complications, not the least of Iwhich is -prehardening of the cement before reaching the joint section.

Considering further, such a cemented connection is relatively permanent and unalterable once installed regardless of the weight load put on the supported structure. Therefore, the grouted joint is usually made excessively long, or over-designed to assure a safe connection, especially where the overall pile length is greater than several hundred feet.

In overcoming the aforementioned problems related to offshore drilling platform supports, the presently disclosed arrangement is provided with specific features to afford greater economy, a more positive wall connection, accuracy of installation, and greater versatility in the use of the offshore facilities. Therefore one object of the invention is to provide a composite foundation member adapted to accurately and economically position an oil producing 0r drilling platform either inland, or in an Patented Jan. 19, 1971 rice offshore body of water. A further object is to provide means for readily installing and locking the anchoring element of the composite foundation member with respect to a platform support leg. Another object is to provide a simple, quickly attainable locking connection between concentrically disposed support and anchor units in a composite foundation member, for an offshore drilling platform positioned above a working surface. A still further object is to provide a firm peripheral joint for a multi-element foundation member in which the use of flowable intermediaries such as cement or the like is precluded.

These and other objects of the invention are afforded by the present arrangement which contemplates the use with an elevated oil drilling structure, of one or more relatively elongated, rigid foundation members, which supportably attach to the str-ucture. More specifically, the disclosed device embodies a plurality of such rigid foundation members which extend from the floor of a body of water such as the ocean, to rigidly support an oil drilling platform above the water surface.

Each foundation member includes two or more concentrically arranged heavy walled, metallic tubular elements the outer element being a casing, the inner element being an anchoring pile. The respective elements are joined at an overlapping portion by a dimpled or outwardly deformed sectionformed of a plurality of discrete indentations in the pile wall which extend radially outward to deform a corresponding section of the casing. The contiguously disposed Walls of the respective units are thereby fixed into a rigid, unrnoving relationship by a common locking joint therebetween through which axial loads applied to the foundation element are transferred,

DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates an elevation view of a leg supported offshore oil well installation in which a segment of one support leg is shown enlarged and in cross section. FIG. 2 is a segmentary view on an enlarged scale of one of the transverse annular joints shown in the leg sections of FIG. l. FIGS. 3ft-3c inclusive are segmentary views on an enlarged scale and in cross section similar to the peripheral joint shown in FIG. 2, illustrating the sequential steps followed in forming a joint of the type disclosed and FIG. 4 is an enlarged segmentary view of a wall deforming element shown in FIG. 2.

Referring to FIG. l, composite foundation member 10 is shown in a substantially upright position. Said member includes in essence, an elongated cylindrical casing 11 which extends normally from a position slightly above the ocean floor, through the body of water, and is operably fastened at its upper end by a clamping mechanism 12 to drilling platform 13. A pile 14, comprising an elongated, open ended cylindrical element, is disposed concentrically Within casing 11, The pile 14 lower end penetrates the ocean floor for a suitable distance to anchor, and rigidly support platform 13 at a predetermined location. The outer dimension of pile 14 is sufficiently large to permit the pile, prior to installation, to slide freely through casing 11 and yet have the outer Walls thereof contiguous with the casing inner wall.

The relatively long casing 11 and inner pile 14, are joined into a unitary, rigid foundation member during initial installation or positioning of platform 13. In a normal drilling platform arrangement, three or more such composite foundation members depend downwardly from platform 13 to provide the necessary stable support to the structure, and to maintain the later in a condition of substantial equilibrium during the drilling operation in spite of weather and water conditions. Y

Casing 11, in accordance with a particular water depth, may extend from the ocean floor to platform 13 for a distance of several hundred feet. However, it is contemplated that with the successful progress in drilling technology, future offshore wells will conceivably .be positioned in 700 to 1,000 feet or more of water. The herein described foundation member is suitably applicable to an offshore platform installation maintained in virtually any water depth so long as the physical capabilities of the composite members are adequate to support the platform load, and resist adverse storm forces.

Referring again to FIG. 1, casing 11 of foundation member is normally fabricated of a series of tubing lengths end welded to achieve a desired length. The diameter and wall thickness of the tubing are physically sufficient to support the platform load at a particular water depth. Since casing 11 upper end is either operatively or fixedly held to platform 13 by clamping arrangement 12, both of which arrangements are familiar to the art, the platform might be positioned either stationarily, or adjusted vertically in the manner of a jack-up arrangement.

'I'he lower end of casing 11 according to preferred practice, terminates a relatively short distance above the ocean floor. Anchor piece or pile 14 extends concentrically within casing 11 lower portion for a suicient distance to afford a structurally safe overlapping load transfer section. Thus, compression loading and bending moment are readily transferred from the elongated casing to the anchor member.

Pile 14 is normally driven into the soft ocean floor by a hammer or similar surface positioned tool to a predetermined depth, or even to an indefinite depth if the composition of the ocean floor is unknown. Therefore, pile 14, which is likewise made up of end-connected tubing lengths, could feasibly extend several hundred feet into the ocean floor as well as up to about 1,000 feet through the casing. In either instance, concentrically disposed casing 11 and pile 14 are joined into a unitary structural member at one or more rigid locking joints near the casing lower end. The number of such joints actually needed is limited only by the physical requirements dictated by a particular installation.

Referring to FIG. 2, inner surface 18 of casing 11 is normally disposed contiguous with outer surface 19 of pile 14 to define an annular space 21 therebetween. The seemingly wide separation of the respective walls as illustrated by FIG. 2 is an exaggeration of the spatial relationship between pile and casing to more clearly delineate the configuration of the wall deformation rather than a proportional annular dimension. The annulus defined by the spaced apart walls facilitates a sliding relationship between the casing and pile during the anchoring operation. However, the Width of annulus 21 as a matter of practicality is minimized to the degree of outward deformation of the inner pile wall, which is essential to deform the outer casing wall. Thus, the annulus width W is sufficiently great to permit lateral deformation of the pile wall at discrete points, to an extent whereby the pile 14 materials elastic limit is exceeded. Further, the pile 14 outer wall 19 is expanded at said discrete points into contact with the casing 11 wall.

Said expansion is achieved lwith a sufficient radial force to at least partially deform the casing to a physical point at which the resulting stress in said casing wall does not exceed the materials elastic limit.

The mutual locking area between pile 14 and casing 11 extends longitudinally of the composite foundation member. The locking area may be limited to the lower end of casing 11 or in the alternative, may constitute two or more l distinct and separated locking areas spaced longitudinally apart. The physical load imposed on the foundation element will determine at least in part the preferred and most efiicient locking arrangement. For example, the length of the locking area in which casing 111 and pile 14 overlap, must be sufficient when subjected to both platform loading and lateral forces induced by weather, water currents, etc., to permit a transfer of stresses between the two fastened elements. However, economically the length of pile 14 disposed within casing 11 is minimized since the pile length disposed upward of the locking area contributes virtually nothing toward the support of platform 13, and but a minimal degree of lateral support in fiexure stress.

For the present description, the locking area is shown as being confined to a particular length of the composite member extending from the lower end of casing 11, upwardly. This locking area as shown in FIGS. 1 and 2, comprises a plurality of discretely disposed dimples 1'6 and 17 formed by a radially outwardly deformed wall section of pile 14. The inner portion of dimple 16 is defined by a generally conically configured cavity 22 at the pile wall inner surface, which terminates at an external arcuate apex 23.

The wall area of casing 14 intermediate apex 23 and the circular base of the cone defined by cavity 22, is severely compressed and usually strained beyond the metals yield point. Thus, the respective dimpled connection points assume a substantially permanent set which will be inwardly deformed only under extreme compressive axial loading on the casing 11 by the platform.

The degree of penetration achieved by apex 23 entering the adjacent inner wall of casing 11, is such that the penetrated area of the latter will not be stressed beyond its elastic limit. Further, the inner radius of apex 19 is suiiiciently large to avoid rupturing the pile internal or external wall under the stress of being permanently deformed.

The penetrating angle A as sho-wn in FIG. 6, is best determined or designed in accordance with optimum penetration to achieve a firm joint. It has been found for example that angle A may be within the range of between 60 and The respective dimples 16 and 17 are disposed both peripherally and longitudinally apart to effect optimum efficiency in the connecting joint. During the step of forming the respective interlocked dimpled halves, a relatively uniform strain on the pile wall is achieved by maintaining a substantially uniform arrangement of the dimples. Thus the latter are disposed preferably in diametrically opposed pairs across the pile diameter and are spaced longitudinally as is required. The disposition of the dimpled points within the locking section of the composite member may comprise a random arrangement of deformations. However, it is preferred in order to assure a more uniform rigidizing area, that the dimples be arranged in a relatively orderly fashion of peripheral rows and vertical lines.

METHOD OF OPERATION In the installation and use of the composite foundation element 10, normally, marine platform 13 is transported or more appropriately, floated to a predetermined location at a drilling site. This would presuppose that the platform is of the type that normally might be towed through the water with legs raised to be at least partially out of the water, and is sufiiciently buoyant to maintain itself afloat. At the site, the respective foundation elements or support legs 10 are lowered from the platform into position. Preferably, such positioning requires that the lower end of the leg be disposed adjacent to but spaced from the ocean oor.

Prior to being transported, pile 14 is prepositioned and removably locked within casing 11 to avoid inadvertently sliding therethrough. At the drilling site, after the foundation elements are lowered into the water to the required depth, pile 14 is released from casing 11 and permitted to guidably descend -by its own weight into the anchoring medium. When such descent has reached its deepest point, by gravity, the pile is forcibly driven to further penetrate into the anchoring medium the required distance.

Under normal circumstances for a particular drilling site, the composition of the ocean oor will be precataloged and as a consequence the ability of the anchoring medium to rmly position a floating platform can be readily determined. Thus, the piling operation is programmed, as to the approximate length of pile required, and the depth to which it will be driven. As a pile forcibly penetrates the anchoring media, additional pile lengths are added to the upper end to maintain said upper end accessible to the pile driver. To most effectively utilize the pile ywith maximum economy, a batter pile might bc used at the upper end of anchorin-g pile 14, and thereafter removed subsequent to imbedment of the latter.

With pile 14 at its optimum holding or imbedded depth, pile 14 and casing 11 are fastened into a unitary member as herein mentioned, by displacing discrete portions of the pile inner wall outwardly into contact with the adjacent casing wall at the locking area. The wall deforming step is achieved by use of an expander unit or tool such as shown in FIGS. 3 to 5. The latter to accomplish its purpose may constitute a number of embodiments but comprises essentially a radial piston cylinder block or tool head 2.6, supported at the lower end of a cable 27 which in turn is supported on a derrick at the water surface. Tool head 26 embodies diametrically aligned passages which guidably retain oppositely positioned pistons `with removable deforming tips 27 and 28. The latter are carried at the remote ends of simultaneously actuated hydraulic pistons 31 and 32 which are horizontally actuatable within the head. Said pistons are reciprocably mounted, and actuated between expanded and withdrawn positions by a pressurized fluid system connected with the respective hydraulic pistons and controlled from the water surface.

Each deforming tip, 27 for example, comprises as noted herein, essentially a conical or similarly shaped hardened metallic member having a convex apex 29 defined by an included angle A of between about 60 and 120 degrees. The tip side surface or surfaces flare outwardly to a peripheral base 33 at the tip broad end, the latter being adapted to be threadably or otherwise removably connected to piston outer end.

With pile 14 imbedded in the ocean substratum to a desired depth, and with head 26 lowered through the pile center, the joint may be quickly formed. Exact positioning of the tool head at the joint area is a matter of choice among any of a number of known methods. With head 26 properly positioned, deforming of the pile walls to obtain a joint of uniform strength is preferably achieved by simultaneously deforming diametrically opposed points radially outward from the pile. Ordinarily, such a force application will create a tendency for the circular pile wall to yield into a non-circular configuration.

Subsequent to a plurality of dimples being formed, and pile and casing being initially rigidized, deforming tips 27 and 28 are retracted into head 26. The latter is thereafter accurately rotated a predetermined degree in accordance with the number of dimples to be formed; the deforming operation is then repeated. While not presently shown, the head may be repositioned by a suitable mechanism such as a remotely controlled drive means together with scanning means associated with the head.

After a peripheral row of dimples is formed, vhead 26 with tips in the withdrawn position, is elevated to a higher level. A second and further series of dimples is then formed. The respective deformations are then continued upward of the pile length to define a locking area of sufcient length to rigidize the casing and the pile to a uniform composite member.

The same operation is performed sequentially on each of the composite anchoring legs. The platform will thus be rigidly supported against the ocean floor on each of its foundation members. Thereafter in the instance of a jack-up type of rig, the platform is adjusted to a desired height preparatory to commencing the drilling operation.

The presently described method embodies numerous advantages over the previous means of making a pile connection by cementing or grouting. In the present arrangement, aside fromv the dirnple locking area no further application of grouting material is required since the locking joint is properly designed, is suiciently rigid to overcome both longitudinal and lateral forces applied to the foundation member.

Other modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof, and therefore, only such limitations should be imposed as are indicated in the appended claims.

Iclaim:

1. A foundation element for supporting a platform above an anchoring medium, said foundation element extending downwardly from said platform and being at least partially imbedded in said anchoring medium, said foundation element including:

an elongated support casing, means in said casing Vdefining an axial guide passage, at least a portion of said means defining said axial guide passage comprising deformable Wall, and

a load supporting anchor piece longitudinally positioned within said guide passage, extending for at least a portion of the casing length, said anchor piece having the lower end thereof adapted for penetration into said anchor medium,

said anchor piece having an outwardly deformable side panel disposed contiguous with the deformable wall portion of said means defining said guide passage, and at least one overlapping locking area rigidly positioning said anchor piece and said casing into a unitary structure, said locking area comprising discretely positioned dimpled sections of said anchor piece deformable panel being outwardly deformed into contact with said casing guide passage deformable wall a sufficient distance for straining said discretely positioned dimpled section of said anchor piece panel beyond the elastic limit thereof and for deforming said casing wall for a degree as to not exceed the elastic limit thereof. 2. In a foundation element as defined in claim 1 wherein said locking area comprises a plurality of dimpled sections disposed circumferentially about the inner wall of said anchor piece.

3. In a found-ation element as defined in claim 1 wherein said locking area dimpled sections are disposed in longitudinal spaced apart relationship one from the other and circumferentially arranged about said anchor piece.

4. Ina foundation element as defined in claim 1 wherein said dimpled sections are arranged in random disposition about the periphery of said anchor piece.

5. Method for locating a marine platform in an elevated position above an anchoring medium, which comprises the steps of:

lotwering at least one foundation support element from said platform to said anchoring medium, said foundation element including an outer cylindrical casing disposed externally of an anchor piece, said respective casing and anchor piece having contiguously disposed walls for permitting sliding movement therebetween,

imbedding the lower end of said anchor piece into said anchoring medium to firmly position the same, and

outwardly deforming the walls of said anchor piece at a plurality of discretely arranged dimpled sections, whereby the outwardly deformed anchor piece will engage and deform the contiguously disposed wall of said casing therebyy to form a joint with the latter to preclude further movement of said anchor piece with respect to said casing.

6. A method for locating a platform in an elevated position above an anchoring medium which comprises the steps of: lowering at least one platform foundation element in a generally upright position from said platform to said anchoring medium, said foundation element including an outer casing and an inner anchor piece, each of said casing and anchor piece having contiguously disposed deformable walls,

rigidly fixing said foundation element outer casing to said platform, and

outwardly deforming said anchor piece at a plurality of discretely disposed points along the surface of the latter, whereby the outwardly deformed anchor piece wall will engage and deform the contiguous surface of said casing and form a contact joint therebetween.

7. In the method as defined in claim 6 wherein said discretely disposed points of said anchor piece are deformed from'the wall of the latter a suicient distance to exceed the elastic limit of said anchor piece material.

8. In the method as defined in claim 7 wherein the deformed portion of said casing wall comprises a dimpled wall section outwardly deformed such that the material thereof is not strained in excess of said materials thereof.

9. In the method as delined in claim 6 including the step of providing discretely disposed dimpled points spaced longitudinally one from the other along said anchoring piece surface.

References Cited UNITED STATES PATENTSi A 277,427 5/1883 l Recht v 294523 2,845,851 8/1958 Pelham .6i-45.5 3,347,053 10/1967 Manning 61-465 3,412,565 11/1968 Lindsey et al.- y61---535 3,453,831 7/1969 Rusche 61-535 JACOB SHAPIRO, Primary Examiner Us. C1. XR. 

